BAND-PASS PIEZOELECTRIC FILTER Russian patent published in 2011 - IPC H03H9/54 

FIELD: radio engineering.

SUBSTANCE: band-pass piezoelectric filter includes three in-series connected piezoelectric resonators (PR) (1-3); to the first output of PR (1) there connected is the first capacitor (C) (4), the second output of which is connected to common bus; to outputs of PR (2) there connected is the second and the third C (5,6), the second outputs of which are connected; to the second output of PR (3) there connected is the fourth C (7) the second output of which is connected to common bus. In addition, there is introduced fifth C (8) connecting the first output of PR (1) to input potential terminal of filter and sixth C (9) connecting the second output of PR (3) to output potential terminal of filter. Besides, to the first output of PR (1) there connected is the first inductance coil (10) the second output of which is connected through the seventh C (11) to the second output of PR (1) and through the eighth C (12) to common bus. The second inductance coil (13) the second output of which is connected through the ninth C (14) to the first output of PR (3) and through the tenth C (15) to common bus is connected to the second output of PR (3). The second outputs of the second and the third C (5,6) are connected through the third inductance coil (16) to common bus.

EFFECT: improvement of filter selectivity and conditions of connection to external devices without using any additional matching circuits.

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